The present invention relates to both a method and a network element for processing signaling data and for controlling connections of subscribers in packet-switching communications networks. A subscriber is connected to a packet-switching communications network. To perform subscriber signaling, signaling information is transmitted between a switching entity and the subscriber.
In the prior art, conventional telecommunications networks have switching nodes; i.e., switching offices or switching systems. These switching nodes include line trunk groups, what is known as peripheral devices, for connecting subscribers or lines, a central computer platform, a message router device and further central units; for example, a switching network, protocol terminating devices of the No. 7 signaling system, background memories and operator devices. A block circuit diagram of such a switching node is illustrated in FIG. 1.
The line trunk groups fulfill essential switching functions which are tied to the voice channels of the line trunk groups. For this reason they contain switching, operating and administrative programs as well as the data information associated with the line trunk groups, such as connection position, signaling, user service classes, call numbers, individual characteristics of connecting lines and subscriber lines, as well as the upgrade level and the configuration of the line trunk group.
The central computer platform is used to coordinate control of the connection setup and of the connection release, as well as the reaction to administrative and fault-induced configuration changes. Peripheral devices are connected to one another and to the common computer platform via the telecommunications system. The further central system components provide the switching system of the switching node with special functions; for example, for connecting through voice channels, for processing signaling protocols, for implementing operator interfaces or for storing mass data. The central components of the switching system are of redundant configuration, i.e. doubled, for example, for reasons of protection against failures. If no increased requirements are made of the switching availability of the subscribers or of the connecting lines of the switching system, the line trunk groups are not of redundant design. However, if stable connections are to be made available above and beyond the failure of one line trunk group, the line trunk groups are also of redundant configuration.
Conventional subscribers of a switching system are connected directly and physically to the line trunk groups or they are connected physically to a subscriber concentrator which is mounted upstream of the line trunk groups and which is connected to the switching office using standardized concentrator interfaces, for example an interface of the V5.X interface series or a TR303 interface, or manufacturer-specific concentrator interfaces, for example a V93 interface or a V95 interface. For voice-channel related connections, signaling data for subscriber signaling and user data is routed via the switching office. The user data is connected through here with a data transmission rate of 64 kbit/s or with a multiple of this data transmission rate. The signaling data for subscriber signaling is transmitted bidirectionally between the subscriber concentrator at the one end and a switching office at the other end for subscriber groups, i.e. jointly for a number of subscribers, using a communications channel according to the definition of the concentrator interface used. In addition to the signaling, end-to-end packet data (user-to-user signaling) or packet data to be passed on to a packet handler interface can be routed in the signaling path in addition to signaling.
In the case of a connection between subscribers of a packet network (for example, voice over packet), the user data is usually not routed to a switching office. The routing of a user data to a switching office is necessary only if a subscriber which is involved in the connection is connected to a conventional circuit-switching communications network, for example a communications network with time-division multiplexing technology, and as a result cannot be reached directly via the packet network. In such a case, it is necessary to convert the user data in order to adapt it to the transmission technology used in the different communications networks. Such a conversion is necessary, in particular, at a junction from a communications network with packet transmission technology with a communications network with time-division multiplexing transmission technology (TDM technology). This conversion is carried out both when transmitting data of the communications network with time-division multiplexing transmission technology to the communications network with packet transmission technology and when transmitting data of the communications network with packet transmission technology to the communications network with time-division multiplexing transmission technology. When there is a telephone connection between two subscribers of a packet network, the user data of the connection is probably exchanged directly via the packet network. In this case, the user data generally is not routed via the switching office using converters or gateways.
In terms of their signaling, the subscribers in the packet network are not associated with a subscriber concentrator or a concentrator interface of a switching office of the circuit-switching communications network via hardware. The subscribers have neither lines for analog signaling nor a D channel for signaling which is routed to a fixed subscriber concentrator which is arranged upstream of a switching office. In the prior art, it is not possible for the signaling for connections between subscribers of a packet-switching communications network also to be carried out for voice connections between the subscribers using a conventional switching office of the circuit-switching communications network. If connection requests of telephone subscribers of a packet network are processed using a switching office or a server which makes available switching functions, the signaling is carried out via the packet network; i.e., the signaling data is transferred in a packet-oriented fashion.
Telephone subscribers in a packet-switching communications network are, for example, subscribers which are connected directly or via a dial-up connection to a network which is based on an Internet protocol. In addition to an Internet access, the subscriber also is provided with the voice services and/or facsimile services. These voice and/or facsimile services are intended to have the same scope of performance as is offered by conventional telephones and facsimile devices. The user data of such a subscriber are transmitted as data packets in accordance with an Internet protocol; for example, in accordance with what is known as the Transmission Control Protocol/User Datagram Protocol (TCP/UDP). Signaling information is transmitted in the packet-switching communications network using signaling packets in accordance with defined standards for example H.323, H.225, H.245, H.450 and SIP.
In packet-switching communications networks, signaling data and user data is transmitted on separate transmission paths. The user data is routed directly to the next subscriber. If it is necessary to convert the user data format, the user data of an interface unit is supplied to a conversion process; for example, a media gateway (MG). The signaling data is supplied, using signaling data packets, to a switching entity which controls connections.
The International Telecommunication Union (ITU) has defined, with its committee ITU-T, the H.323 Standard for data transmission in IP-based communications networks. The H.323 Standard provides and defines components, such as terminals, gateways, gatekeepers and multipoint control units, which are involved in such a connection. A H.323 terminal corresponds to the subscriber of the packet-switching communications network. Gateways are then used if the connection has to be routed via, for example, a public telephone network or if one party to the call is a subscriber connected to a switching office of the public telephone network. Multipoint control units are provided in order to set up conferencing circuits, for example.
The gatekeeper is the central component involved in the connection setup. It can be regarded as a switching office in the packet-switching communications network. The gatekeeper provides its zone with functions which serve, inter alia, for performing access monitoring, signaling, connection control and toll metering. The gatekeeper is also used for the call number assignment (E.164) to the subscriber address which is valid for the subscriber of the packet-switching communications network, the assignment (E.164) being necessary for access to the public telephone network. In a communications network which is based on the Internet protocol, what is referred to as an IP network, the address of the subscriber is the IP address. Thus, the gatekeeper is not a switching office of a public telecommunications network but rather a control unit in the IP-based communications network. Such a control unit is, for example, a server.
If network operators of circuit-switching communications networks also want to provide subscribers of packet-switching communications networks with communications services. In order to acquire new customers, these network operators must purchase novel technical equipment. This novel technical equipment has properties which are different from those of conventional switching offices; for example, with respect to the failure characteristics and performance, other standards of operation and toll metering and other manufacturers. As a result, the network operator incurs not only considerable procurement costs but also additional operating costs; for example, for instructing operating personnel. The high level of availability of the novel technical equipment and the implementation of both service features and features such as known toll metering standards can be achieved only with considerable financial outlay, if at all.
If a conventional switching office of a circuit-switching communications network is to carry out the connection control or the processing of signaling data for subscribers of a packet-switching communications network, the packet-network-specific signaling methods which are relevant to the subscriber signaling must be implemented in the switching office. Furthermore, signaling access to the packet-switching communications network must be implemented in the switching office, and software access to the subscribers of the packet-switching communications network must be ensured. These completely novel requirements of a conventional switching office require costly adaptation and restructuring of hardware components and software components. Considerable development expenditure is necessary to carry out these changes and restructuring operations.
An object of the present invention, therefore, is to disclose a method and a network element which easily use a network element of a circuit-switching communications network for performing subscriber signaling of subscribers of a packet-switching communications network.